The invention relates to a microprocessor-based trip device for an electrical circuit breaker, comprising:
current detection means, generating analog signals representative of the currents flowing in the conductors protected by the circuit breaker,
analog to digital conversion means to which the analog signals are applied and which supply corresponding digital signals,
a microprocessor-based digital processing unit to which the digital signals are applied to perform at least standard long delay and/or short delay tripping functions and which generates a circuit breaker tripping order when preset parameters are exceeded, said unit comprising a keypad for an operator to enter the tripping parameters, display means, a random-access memory and a read-only memory connected to the microprocessor, the read-only memory comprising a plurality of subroutines corresponding to the standard functions and to a plurality of optional functions of the trip device,
means enabling certain optional functions to be selected,
and circuit breaker tripping means actuated by the tripping order.
In state-of-the-art microprocessor-based trip devices of the type mentioned above, selection of the optional functions is achieved by means of electrical contacts, for example microswitches, whose position is representative of the options selected.
It has also been proposed (U.S. Pat. No. 4,694,373) to fit several different non-volatile memories for each trip device, each memory associated with a possible option, choice of the option being made by fitting the relevant memory in the trip device.